Question

can anyone tell me the answer of the 13th question

Answer 1

If plaster of Paris is exposed to air it just takes the moisture in air and becomes gypsum again.

That is
CaSO4.1/2H2O + 3/2H2O -------> CaSO4.2H2O.
Gypsum is hard and does not posses the qualities of plaster of Paris.
Therefore to maintain it's properties its kept in dry container free of moisture.


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- Maheshwaran.